There are several problems in the global building construction industry, such as increasing environmental impact due to growing demand and production of energy, increases in cost of energy consumption, mandatory compliance to new and tougher building energy codes and legislation, increasing impact of climate change and natural disasters, including cyclones, tsunamis and bush fires, all of which are predicted to continue to grow into the future.
A significant source of energy consumption is in the heating and cooling of buildings and one way to combat the increasing cost and environmental impact of energy production is to make buildings more thermally efficient so that they use energy more efficiently.
Accordingly, buildings of the future need to be super strong to withstand the vagaries of nature and highly thermally energy efficient, whilst maintaining exceptional occupant comfort.
Conventional building technologies tend not to be energy efficient and not to comply to increasingly stringent energy codes and legislation.
Super insulation is an approach to building design and construction that dramatically reduces heat loss (and gain) by using much higher levels of insulation and air tightness than is conventional. Super insulation is one of the key elements of the passive house design approach.
A super insulated building is intended to reduce heating needs very significantly, and may be heated predominantly by intrinsic heat sources (waste heat generated by appliances and body heat of occupants) with only a very small amount of actively generated backup heat being required to maintain occupant comfort. In addition to requiring little or no actively generated heat to moderate the temperature of the building interior, a super insulated building also takes longer to cool in the event of an extended power failure during cold weather, for example after a severe ice storm disrupts electric transmission, because heat loss is much less than normal buildings, without compromising on thermal storage capacity.
The additional cost of super insulation is offset by a reduction in size and capital cost of heating and cooling systems required for a building, along with drastic reductions in ongoing heating and cooling energy consumption and costs.
The human body perceives temperature in several ways. Air temperature, air movement, and room surface temperatures all affect how we feel in a space. A super-insulated building shell addresses comfort by limiting the movement of air and increasing room surface temperatures at a given room air temperature. Meticulous efforts to increase insulation and reduce air leakage within the building envelope facilitate occupants feeling much more comfortable within the building and a reduction in energy usage/operating costs.
Heat losses through external walls account for more than 40% of the total heat losses in buildings. Therefore, improving thermal insulation of external walls is a highly effective way to save energy. In low-energy buildings, the entire building envelope can be super insulated. The building envelope consists of all the building elements that separate the building interior from the exterior environment. A major purpose of superinsulation is to provide a comfortable indoor climate, irrespective of the outdoor climate which is affected by the weather. However, restricting heat flow in any building, irrespective of the climate, can improve its energy efficiency. In summary, quality super insulation can facilitate affordable energy savings.
For the past century, reinforced concrete has been the preferred choice for constructing buildings because of its very high structural strength, which results in solid, strong and durable building structures that are better suited to withstand severe cyclonic weather conditions and have superior ability to withstand hush fires and other natural disasters. However, people often perceive concrete to be a cold unfriendly material, and concrete buildings to be uncomfortable to live in because they get very cold in the winter and very hot in the summer. Accordingly, people perceive concrete buildings to be expensive to heat and cool.
One way to improve the energy efficiency and comfort levels of a concrete building is to super insulate its concrete walls, which dramatically improves the thermal performance of the building and makes it highly energy efficient by reducing energy consumption required for heating and cooling.
Passive House standards typically require sufficient insulation to achieve a U-Value of 0.11 W/(m2K) or an equivalent R-Value of R 9.
Currently available concrete wall systems are not able to meet the Passive House standards because they are unable to achieve the required insulation thickness. Moreover, poor design of currently available concrete wall systems creates thermal bridges, which disadvantageously allow heat energy to bypass the insulation and pass through the wall, again preventing compliance with Passive House standards. Thermal bridges can also cause condensation, which can lead to mold growth and moisture damage. Elimination of thermal bridges is therefore critical to maintaining building air quality and durability, as well as to achieving the necessary levels of super insulation required for Passive House compliance.
There are very few modular systems available for forming of super insulated structural concrete walls. Accordingly, builders tend to form super insulated structural concrete walls using conventional poured in place methods with removable formwork, which is subsequently stripped to allow insulation to be installed, or with stay in place insulated concrete form systems commonly known as ICFs. Both these options have severe technical and commercial drawbacks and are very labour intensive and expensive.
In conventional poured-in-place construction with removable formwork, a crew erects spaced apart inner and outer forms of plywood, steel, or aluminum that define a cavity therebetween for receiving wet concrete. After placing rebar in the cavity to reinforce the wall, the crew pours concrete inside the cavity. Once the concrete hardens, the crew strips the forms to leave the reinforced concrete walls. Insulation is then mechanically attached to the walls as a secondary operation by using construction anchors, which is a very time consuming and labour intensive process. The installation of insulation is also prone to defects, such as gaps and thermal bridging, which limit the overall insulation performance of the wall. Some systems use plastic anchors to secure the insulation to the concrete wall, but none of the commercially available plastic anchors are long enough or structurally strong enough to secure insulation of the thickness required to meet Passive House standards. Another disadvantage with conventional systems is that there is no provision for attaching external cladding to the insulation. Accordingly, builders have to install timer batons on the exterior of the insulation and affix the batons using long metal screws extending through the insulation and into the concrete core. These screws act as thermal bridges, which result in the disadvantages mentioned above.
Known ICFs are made of foam insulation and, unlike removable forms, are designed to stay in place as a permanent part of the wall assembly. ICFs typically comprise expanded polystyrene foam sheets with a thickness of about 50 mm (2 inches). The ICF sheets on each side of the forming cavity are held together by plastic or metal ties and are stacked and interlocked one on top of the other, almost like children's building blocks. The internal and external ICF layers therefore provide a total insulation thickness of only 100 mm (4 inches), providing a total R-Value of only R3, which is well below the insulation thickness of 350 mm (14 inches) required to provide an R-Value of R9 to meet Passive House standards. The use of metal ties also introduces thermal bridges, which result in the disadvantages mentioned above. Another disadvantage of ICFs is that it is not possible to leave the interior side of the concrete core free of insulation, which can provide enhanced thermal performance in certain circumstances, and which facilitates installing fiber cement, magnesium oxide, calcium silicate or other dry wall material sheets on the interior side of the concrete core. Another drawback with ICFs is that they use shape moulded expanded polystyrene beads, which have very poor thermal, fire and structural ratings and do not meet the high performance criteria for buildings of the future. The shape moulding process does not allow the use of different types of high performance sheet based insulation materials, such as extruded polystyrene, polyurethane, polyisocyanurate (PIR) or phenolic insulation materials. Another drawback is the presence of a large number of joints, both horizontal and vertical, in the insulation, which result in leakage of air and thermal energy and reduce the overall insulation value of the building, as well as allowing water and moisture ingress. Another drawback is that it is difficult to build corners in any desired angles with ICFs, and builders often have to resort to manual forming to build corners, which is both time consuming and expensive. Another drawback with ICFs is that they are not strong enough for the attachment of heavy weight external cladding such as bricks, stone, fiber cement or similar heavy weight materials, and do not have any structural system which can transfer the weight of the heavy exterior cladding to the concrete core without forming a thermal bridge. Some known ICFs have plastic webs for the attachment of external cladding using screws. However, the webs do not have enough screw pull out resistance to handle negative wind pressure in high winds and cyclone conditions, and the screws also loosen over time, which leads to sagging of the external cladding. Another drawback with known ICFs is that they are not suitable for extended fire rating situations and cannot be used in egress paths or other high risk areas of buildings. Another problem with known ICFs is water seeping through exterior stucco or render finishes and remaining embedded in the external insulation layer for extended periods of time, causing long term condensation and mould growth problems. Another drawback with many known ICFs is that they require external covering and finishing on site, which is very labour intensive and expensive. Another drawback with many known ICFs is that the internal and external insulation layers are installed prior to the installation of steel reinforcement for the concrete core, which makes it virtually impossible to tie the vertical reinforcement to the starter bars, which can seriously compromise the structural integrity of the wall, and to check and inspect the reinforcement prior to pouring the concrete core. Another drawback with known ICFs is that concrete footings for the wall need to be manually formed, which in not only very labour intensive and expensive but also makes it very difficult to level the wall with the footings. Moreover, providing adequate structural connection between known ICF walls and their footings can be very difficult and time consuming.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.